REPRODUCIBILITY,
VARIABILITY,
RELIABILITY
of
CMOS IMAGE SENSORS

Newly obtained quantitative data and technical report by Harvest Imaging.

A new Harvest Imaging project is started that will generate technical data about CMOS image sensors concerning the reproducibility, variability and reliability of the performance characteristics. This kind of information has never been published before. None of the CMOS image sensor vendors is supplying numerical information about reproducibility, variability and reliability of their devices. So if the vendors do not supply this data, only measurements on existing products can reveal the “secrets”.

Reproducibility, variability and reliability of the sensors are crucial characteristics for the camera manufacturer. In the case the camera producer wants to use a single set of camera calibration parameters for all sensors of a particular type, all sensors need to perform in the same way, and need to have stable characteristics over time. Is this the case in reality ? How well do various sensors match to each other ? How stable are the sensor performance characteristics over time ? Do sensors age ?

In this Harvest Imaging project the reproducibility, the variability and the reliability of the CMOS imagers will be analyzed :

• Reproducibility : will give quantitative information about how well particular measurements and retrieved performance data do reproduce if the devices are measured over and over again by means of the same calibrated measurement equipment,
• Variability : will give quantitative information about the spread of the performance data from sensor to sensor/from camera to camera,
• Reliability : will give quantitative information about the stability of the sensor and camera performance over time.

The measurements are done on a higher-end, more expensive camera with a global shutter CMOS sensor and on a lower-end, cheaper camera with a rolling shutter CMOS sensor. The cameras will be thoroughly measured every 6 months over a period of 5 years.

In the following sections of this document, the content of the reproducibility, variability and reliability will be further detailed.

REPRODUCIBILITY

To characterize and evaluate the reproducibility of the measurements, all cameras are 10 times mesasured by means of a calibrated set-up. The various tests and the measured parameters are listed below.

The reproducibility test is repeated every 6 months over a period of 5 years, starting in the first quarter of 2017. The chapter in the report about the reproducibility will contain statistical data of all parameters characterized. Reporting about the reproducibility is done once every year, starting mid-2017.

VARIABILITY

To characterize and evaluate the variability between various cameras of the same vendor and with the same sensor, all cameras are 10 times measured by means of a calibrated set-up. The various tests and the measured parameters are listed below.

All parameters of all cameras will be available which does allow studying how the camera and sensor characteristics differ from camera to camera. This variability analysis of all the parameters characterized will be described in the report. The overall study of the variability is repeated every 6 months over a period of 5 years, starting in the first quarter of 2017. Reporting about the reproducibility is done once every year, starting mid-2017.

RELIABILITY

To characterize and evaluate the reliability of various cameras of the same vendor and with the same sensor, all cameras are 10 times measured by means of a calibrated set-up. The various tests and the measured parameters are listed below.

All parameters of all cameras will be available which does allow to study how the camera and sensor characteristics will change over time. This reliability analysis of all the parameters characterized will be described in the report. The overall analysis of the reliability is repeated every 6 months over a period of 5 years, starting in the first quarter of 2017. Reporting about the reliability is done once every year, starting mid-2017. In a first stage of the reliability study the sensors will simply be stored on the shelf. In a second stage of the reliability, starting after one year (= after 3 measurement cycles), the sensors will be extra stressed, such as :

• Temperature – humidity stress at 85 °C – 85 % humidity,
• Stored under UV-light to test the stability of the colour filters,
• Exposed to gamma-rays,
• Exposed to cosmic rays at higher altitudes,
• ….

Subsequent measurement cycles will give quantitative data about the reliability of the sensors under harsh conditions.

TESTS PERFORMED, PARAMETERS CHARACTERIZED

To analyze the reproducibility, variability and reliability of the sensors, the following tests are performed and the listed parameters are characterized :

• Two sets, each of 16 cameras :
  • with a global shutter CMOS sensor,
  • with a rolling shutter CMOS sensor,
• All cameras are 10 times measured by means of a calibrated set-up,
• For every camera, the following parameters are characterized :
  • According to the EMVA1288 standard :
    • Conversion gain,
    • QE for B (466nm), G (532nm), R (630nm) and n-IR (850 nm),
    • Dark noise,
    • Dark signal non-uniformity,
    • Maximum SNR,
    • PRNU for B (466 nm), G (532 nm), R (630 nm) and n-IR (850 nm),
    • Non linearity for B (466 nm), G (532 nm), R (630 nm) and n-IR (850 nm),
    • Sensitivity threshold for B (466 nm), G (532 nm), R (630 nm) and n-IR (850 nm),
    • Saturation capacity,
    • Dynamic range,
    • Dark current.
  • Additional measurements beyond EMVA1288 standard :
    • At 0s exposure time :
      • Fixed-pattern noise (total, pixel, column, row),
      • Maximum average pixel value in every column,
      • Maximum average pixel value in every row,
      • Pixel with highest temporal noise in every column,
      • Pixel with highest temporal noise in every row,
    • At 1s exposure time :
      • Fixed-pattern noise (total, pixel, column, row),
      • Maximum average pixel value in every column,
      • Maximum average pixel value in every row,
      • Pixel with highest temporal noise in every column,
      • Pixel with highest temporal noise in every row,

COST AND TIMING

For those who are interested to acquire the report, one has the choice to :

• OR, only buy the reports of the global shutter sensor,
• OR, only buy the reports of the rolling shutter sensor,
• OR, buy the total set of both sensor,
• for each abovementioned possibility, the option exist to buy the standard technical report OR the extended version of the technical report. The extended version of the report will have the content of the standard report plus in addition all images acquired during the non-EMVA1288 measurements.

The yearly (extended) reports will become available in the Summer of each calendar year (Summer ’17, Summer ’18, Summer ’19, Summer ’20 and Summer ’21). A customer can step into this project at any given time, but the earlier the more attractive the pricing of the report(s) will be. Once a customer has stepped into the project, he/she will automatically receive all reports that are produced AFTER the date he/she stepped in.

More information needed, please fill out the form below :